The processes for the forming of sheet metal currently include the brake press forming of fold lines (or folding about fold lines with a folding machine), roll forming, or pressing either between two dies, one of which is male and the other female, or alternatively, pressing with a female die and rubber contained in a container to function as a semi-fluid and effect the pressing.
Roll forming and brake pressing is usually limited to the formation of constant cross-sectional shape articles, although it is known to have serrated or otherwise formed rollers on roll forming machines for effecting transverse as well as longitudinal deformation of the workpiece. Simple serrated rollers are relatively inexpensive, but rollers having more complex patterns thereon, for example, to provide a checker-plate effect, are very expensive and for this reason are not commonly used. As indicated in U.S. Pat. Nos. 2,280,359 TRUDELL and 2,966,873 HOFFMAN, it is known to press sheet metal against rubber in a large press, but many practical problems are encountered because of the huge presses required. For example, to press a two meter by one meter sheet of metal to a checker-plate configuration utilising the rubber male die technique would require a press of approximately 12000 ton capacity, a very large slab of rubber, and a container for containing the rubber around its edges when it functions as a semi-fluid during the pressing operation.
In the U.S. Pat. No. 2,528,540 OLDOFREDI there are described and illustrated two methods of ornamenting sheet metal, one of which incorporates a slab of rubber in a press and the other a rubber coated roller. The press arrangement is subject to the abovementioned disability of high pressure requirement, and experiments conducted by the inventor herein have established that a rubber covered roller is subject to the very serious disability that the peripheral length of the rubber greatly increases when high pressure applied against a workpiece reduces the radial thickness of the rubber at that point.
The closest prior art known to the inventor is the abandoned Australian application No. 43127/64 in the name of John Lysaght (Australia) Limited, wherein one embodiment suggested the use of a die sheet on which was placed a workpiece and a slab of cushioning material, the "sandwich" being passed between driven rollers, and supported front and rear on idler rollers of respective roll cases. Experiments have indicated that this process is suitable for embossing. thin sheet metal workpieces. It does not appear to be suitable for embossing or shearing thick metal workpieces (say above 0.040 inches or 1 mm. thickness), since the bending loads applied to a relatively unsupported die plate and carriage by the elastomer in front of and to the rear of the nip of the rollers impose such a heavy load that, either the die plate and carriage will bend, or the die plate and carriage will be of such size and weight that only low production rates will be achieved.
The main object of this invention is to provide a simple process and machine for the forming of sheet metal wherein transverse as well as longitudinal deformations may be effected, not only in very thin sheet metal, but in metal of a thickness which is useful for a wide range of applications, for example, in thicknesses greater than 0.020 inches or 0.5 mm.